Methods for inhibiting neuronal damage

ABSTRACT

A method for inhibiting neuronal damage due to hypoglycemia comprising administering to a human in need thereof an effective amount of a compound having the formula ##STR1## wherein R 1  and R 3  are independently hydrogen, --CH 3 , ##STR2## wherein Ar is optionally substituted phenyl; R 2  is selected from the group consisting of pyrrolidine, hexamethyleneamino, and piperidino; or a pharmaceutically acceptable salt of solvate thereof.

BACKGROUND OF THE INVENTION

It has been observed that one of the most important side effects of people inflicted with debilitating conditions resulting from the uncontrolled regulation of sugar metabolism, is slow but progressive deterioration of neurons in the brain, This deterioration of neuronal function often leads to debilitation of these people to take care of themselves and a loss of ability to conduct normal lives. This loss of function not only leads to loss of personal well being, but also causes economic hardship due the need of extended custodial care. One of the most important syndromes leading to neuronal damage, is diabetes. Although the most common consideration in the treatment of the diabetic is that of hyperglycemia, there are many instances during the course of insulin treatment which involve hypoglycemia, i.e., too much insulin, leading to low blood glucose and starvation of tissues and organs from the glucose needed for proper function. These incidents of hypoglycemia are becoming more common with the introduction of new regiments of insulin administration. The latest protocols for insulin administration advocate a tighter schedule and more frequent use of insulin to better control the risk of hyperglycemia. As a result of this tighter control of blood glucose, more incidents of hypoglycemia are being reported. Another, though less common cause of hypoglycemia in the diabetic, is the use of oral agents such as the sulfonylureas. To date, there are no effective treatments to counter this neuronal damage, other than to attempt to more carefully regulate blood glucose levels, which has not been entirely successful.

Recently, there have been reports in the literature that one of the effects of estrogens on the brain and central nervous system is the regulation of glucose utilization. The implication from this work would be that the use of estrogen may be beneficial in protecting the patient from neuronal damage due to hypoglycemic incidents. However, the possible use of estrogen for neuronal protection is not without its detrimental side effects most notably the effect of estrogen on the sex tissues (breast and uterus) in women and preclusion of its use in men. So, although the administration of estrogen may have great potential in ameliorating the neuronal damage due to hypoglycemia, its use may be severely limited by its side effects. Clearly, a better therapy would be of great benefit.

SUMMARY OF THE INVENTION

This invention provides methods of inhibiting neuronal damage due to hypoglycemia comprising administering to a human in need thereof an effective amount of a compound of formula I ##STR3## wherein R¹ and R³ are independently hydrogen, --CH₃, ##STR4## erein Ar is optionally substituted phenyl;

R² is selected from the group consisting of pyrrolidino, hexamethyleneimino, and piperidino; and pharmaceutically acceptable salts and solvates thereof.

DETAILED DESCRIPTION OF THE INVENTION

The current invention concerns the discovery that a select group of 2-phenyl-3-aroylbenzothiophenes (benzothiophenes), those of formula I, are useful for inhibiting neuronal damage due to hypoglycemia.

The therapeutic and prophylactic treatments provided by this invention are practiced by administering to a human in need thereof a dose of a compound of formula I or a pharmaceutically acceptable salt or solvate thereof, that is effective to inhibit neuronal damage due to hypoglycemia or its symptoms.

The term "inhibit" includes its generally accepted meaning which includes prohibiting, preventing, restraining, and slowing, stopping or reversing progression, severity or a resultant symptom. As such, the present method includes both medical therapeutic and/or prophylactic administrations as appropriate.

Raloxifene is a preferred compound of this invention and it is the hydrochloride salt of a compound of formula 1 wherein R¹ and R³ are hydrogen and R² is 1-piperidinyl. Raloxifene has been shown to bind to estrogen receptor and was originally thought to be a molecule whose function and pharmacology was that of an anti-estrogen in that it blocked the ability of estrogen to activate uterine tissue and estrogen dependent breast cancers. Indeed, Raloxifene does block the action of estrogen in some cells; however, in other cell types, Raloxifene activates the same genes as estrogen does and displays the same pharmacology, e.g., osteoporosis, hyperlipidemia, etc. As a result, Raloxifene has been referred to as an anti-estrogen with mixed agonist-antagonist properties. The unique profile which Raloxifene displays and differs from that of estrogen is now thought to be due to the unique activation and/or suppression of various gene functions by the Raloxifene-estrogen receptor complex as opposed to the activation and/or suppression of genes by the estrogen-estrogen receptor complex. Therefore, although Raloxifene and estrogen utilize and compete for the same receptor, the pharmacological outcome from gene regulation of the two is not easily predicted and is unique to each.

Generally, at least one compound of formula I is formulated with common excipients, diluents or carriers, and compressed into tablets, or formulated as elixirs or solutions for convenient oral administration, or administered by the intramuscular or intravenous routes. The compounds can be administered transdermally, and may be formulated as sustained release dosage forms and the like.

The compounds used in the methods of the current invention can be made according to established procedures, such as those detailed in U.S. Pat. Nos. 4,133,814, 4,418,068, and 4,380,635 all of which are incorporated by reference herein. In general, the process starts with a benzo b!thiophene having a 6-hydroxyl group and a 2-(4-hydroxyphenyl) group. The starting compound is protected, acylated, and deprotected to form the formula I compounds. Examples of the preparation of such compounds are provided in the U.S. patents discussed above. The term "optionally substituted phenyl" includes phenyl and phenyl substituted once or twice with C₁ -C₆ alkyl, C₁ -C₄ alkoxy, hydroxy, nitro, chloro, fluoro, or tri(chloro or fluoro)methyl.

The compounds used in the methods of this invention form pharmaceutically acceptable acid and base addition salts with a wide variety of organic and inorganic acids and bases and include the physiologically acceptable salts which are often used in pharmaceutical chemistry. Such salts are also part of this invention. Typical inorganic acids used to form such salts include hydrochloric, hydrobromic, hydroiodic, nitric, sulfuric, phosphoric, hypophosphoric and the like. Salts derived from organic acids, such as aliphatic mono and dicarboxylic acids, phenyl substituted alkanoic acids, hydroxyalkanoic and hydroxyalkandioic acids, aromatic acids, aliphatic and aromatic sulfonic acids, may also be used. Such pharmaceutically acceptable salts thus include acetate, phenylacetate, trifluoroacetate, acrylate, ascorbate, benzoate, chlorobenzoate, dinitrobenzoate, hydroxybenzoate, methoxybenzoate, methylbenzoate, o-acetoxybenzoate, naphthalene-2-benzoate, bromide, isobutyrate, phenylbutyrate, β-hydroxybutyrate, butyne-1,4-dioate, hexyne-1,4-dioate, caprate, caprylate, chloride, cinnamate, citrate, formate, fumarate, glycollate, heptanoate, hippurate, lactate, malate, maleate, hydroxymaleate, malonate, mandelate, mesylate, nicotinate, isonicotinate, nitrate, oxalate, phthalate, teraphthalate, phosphate, monohydrogenphosphate, dihydrogenphosphate, metaphosphate, pyrophosphate, propiolate, propionate, phenylpropionate, salicylate, sebacate, succinate, suberate, sulfate, bisulfate, pyrosulfate, sulfite, bisulfite, sulfonate, benzene-sulfonate, p-bromophenylsulfonate, chlorobenzenesulfonate, ethanesulfonate, 2-hydroxyethanesulfonate, methanesulfonate, naphthalene-1sulfonate, naphthalene-2-sulfonate, p-toluenesulfonate, xylenesulfonate, tartarate, and the like. A preferred salt is the hydrochloride salt.

The pharmaceutically acceptable acid addition salts are typically formed by reacting a compound of formula I with an equimolar or excess amount of acid. The reactants are generally combined in a mutual solvent such as diethyl ether or benzene. The salt normally precipitates out of solution within about one hour to 10 days and can be isolated by filtration or the solvent can be stripped off by conventional means.

Bases commonly used for formation of salts include ammonium hydroxide and alkali and alkaline earth metal hydroxides, carbonates, as well as aliphatic and primary, secondary and tertiary amines, aliphatic diamines. Bases especially useful in the preparation of addition salts include ammonium hydroxide, potassium carbonate, methylamine, diethylamine, ethylene diamine and cyclohexylamine.

The pharmaceutically acceptable salts generally have enhanced solubility characteristics compared to the compound from which they are derived, and thus are often more amenable to formulation as liquids or emulsions.

Pharmaceutical formulations can be prepared by procedures known in the art. For example, the compounds can be formulated with common excipients, diluents, or carriers, and formed into tablets, capsules, suspensions, powders, and the like. Examples of excipients, diluents, and carriers that are suitable for such formulations include the following: fillers and extenders such as starch, sugars, mannitol, and silicic derivatives; binding agents such as carboxymethyl cellulose and other cellulose derivatives, alginates, gelatin, and polyvinyl pyrrolidone; moisturizing agents such as glycerol; disintegrating agents such as calcium carbonate and sodium bicarbonate; agents for retarding dissolution such as paraffin; resorption accelerators such as quaternary ammonium compounds; surface active agents such as cetyl alcohol, glycerol monostearate; adsorptive carriers such as kaolin and bentonire; and lubricants such as talc, calcium and magnesium stearate, and solid polyethyl glycols.

The compounds can also be formulated as elixirs or solutions for convenient oral administration or as solutions appropriate for parenteral administration, for instance by intramuscular, subcutaneous or intravenous routes. Additionally, the compounds are well suited to formulation as sustained release dosage forms and the like. The formulations can be so constituted that they release the active ingredient only or preferably in a particular part of the intestinal tract, possibly over a period of time. The coatings, envelopes, and protective matrices may be made, for example, from polymeric substances or waxes.

The particular dosage of a compound of formula I required to inhibit neuronal damage due to hypoglycemia according to this invention will depend upon the severity of the condition, the route of administration, and related factors that will be decided by the attending physician. Generally, accepted and effective daily doses will be from about 0.1 to about 1000 mg/day, and more typically from about 50 to about 200 mg/day. Such dosages will be administered to a subject in need thereof from once to about three times each day, or more often as needed, and for a duration sufficient to effectively prevent neuronal damage.

It is usually preferred to administer a compound of formula I in the form of an acid addition salt, as is customary in the administration of pharmaceuticals bearing a basic group, such as the piperidino ring. For such purposes the following oral dosage forms are available.

FORMULATIONS

In the formulations which follow, "Active ingredient" means a compound of formula I.

Formulation 1: Gelatin Capsules

Hard gelatin capsules are prepared using the following:

    ______________________________________     Ingredient        Quantity (mg/capsule)     ______________________________________     Active ingredient   0.1-1000     Starch, NF         0-650     Starch flowable powder                        0-650     Silicone fluid 350 centistokes                        0-15     ______________________________________

The ingredients are blended, passed through a No. 45 mesh U.S. sieve, and filled into hard gelatin capsules.

Examples of specific capsule formulations of raloxifene that have been made include those shown below:

Formulation 2: Raloxifene capsule

    ______________________________________     Ingredient        Quantity (mg/capsule)     ______________________________________     Raloxifene        1     Starch, NF        112     Starch flowable powder                       225.3     Silicone fluid 350 centistokes                       1.7     ______________________________________

Formulation 3: Raloxifene capsule

    ______________________________________     Ingredient        Quantity (mg/capsule)     ______________________________________     Raloxifene        5     Starch, NF        108     Starch flowable powder                       225.3     Silicone fluid 350 centistokes                       1.7     ______________________________________

Formulation 4: Raloxifene capsule

    ______________________________________     Ingredient        Quantity (mg/capsule)     ______________________________________     Raloxifene        10     Starch, NF        103     Starch flowable powder                       225.3     Silicone fluid 350 centistokes                       1.7     ______________________________________

Formulation 5: Raloxifene capsule

    ______________________________________     Ingredient        Quantity (mg/capsule)     ______________________________________     Raloxifene        50     Starch, NF        150     Starch flowable powder                       397     Silicone fluid 350 centistokes                       3.0     ______________________________________

The specific formulations above may be changed in compliance with the reasonable variations provided.

A tablet formulation is prepared using the ingredients below:

Formulation 6: Tablets

    ______________________________________     Ingredient       Quantity (mg/tablet)     ______________________________________     Active ingredient                        0.1-1000     Cellulose, microcrystalline                       0-650     Silicon dioxide, fumed                       0-650     Stearate acid     0-15     ______________________________________

The components are blended and compressed to form tablets.

Alternatively, tablets each containing 0.1-1000 mg of Active ingredient are made up as follows:

Formulation 7: Tablets

    ______________________________________     Ingredient          Quantity (mg/tablet)     ______________________________________     Active ingredient   0.1-1000     Starch              45     Cellulose, microcrystalline                         35     Polyvinylpyrrolidone                         4     (as 10% solution in water)     Sodium carboxymethyl cellulose                         4.5     Magnesium stearate  0.5     Talc                1     ______________________________________

The Active ingredient, starch, and cellulose are passed through a No. 45 mesh U.S. sieve and mixed thoroughly. The solution of polyvinylpyrrolidone is mixed with the resultant powders which are then passed through a No. 14 mesh U.S. sieve. The granules so produced are dried at 50°-60° C. and passed through a No. 18 mesh U.S. sieve. The sodium carboxymethyl starch, magnesium stearate, and talc, previously passed through a No. 60 U.S. sieve, are then added to the granules which, after mixing, are compressed on a tablet machine to yield tablets.

Suspensions each containing 0.1-1000 mg of Active ingredient per 5 mL dose are made as follows:

Formulation 8: Suspensions

    ______________________________________     Ingredient          Quantity (mg/5 ml)     ______________________________________     Active ingredient    0.1-1000  mg     Sodium carboxymethyl cellulose                          50        mg     Syrup                1.25      mg     Benzoic acid solution                          0.10      mL     Flavor               q.v.     Color                q.v.     Purified water to    5         mL     ______________________________________

Active ingredient is passed through a No. 45 mesh U.S. sieve and mixed with the sodium carboxymethyl cellulose and syrup to form a smooth paste. The benzoic acid solution, flavor, and color are diluted with some of the water and added, with stirring. Sufficient water is then added to produce the required volume.

ASSAY

Twenty patients are selected who have either been subjected to episodes of hypoglycemia or are thought to be at risk of such episodes due to the use of insulin or oral hyperglycemic agents. These patients are administered 50-200 mg of a compound of this invention as an oral dose (single or split) on a daily basis. These patients are closely monitored for signs of neuronal deterioration over the course of one year. Common signs of neurological damage which would be noted are: nervousness, tremors, sweating, unusual hunger, confusion, abnormal behavior, loss of consciousness, and convulsion. The profile of these treated patients would be compared to a matched set of control patients receiving a placebo. A positive result would be a decrease in the number of such symptoms in the treated group compared to those in the control group.

Utility of the compounds of formula I is illustrated by the positive impact they have in the assay described above. 

I claim:
 1. A method of inhibiting central nervous system neuronal damage due to hypoglycemia comprising administering to a human in need thereof an effective amount of a compound having the formula ##STR5## wherein R¹ and R³ are independently hydrogen, --CH₃, ##STR6## herein Ar is optionally substituted phenyl; R² is selected from the group consisting of pyrrolidine, hexamethylenemino, and piperidino; or a pharmaceutically acceptable salt of solvate thereof.
 2. The method of claim 1 wherein said compound is the hydrochloride salt thereof.
 3. The method of claim 1 wherein said administration is prophylactic.
 4. The method of claim 1 wherein said compound ##STR7## or its hydrochloride salt. 